<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
			<p><input placeholder="半径" type="text" id="a"></p>
			<p><input placeholder="周长" type="text" id="b"></p>
			<p><input placeholder="面积" type="text" id="c"></p>
		
		<script>
			var p = Math.PI;
			var t = prompt("输入圆的半径");
			var zc = t * 2 * p;
			var mj = t * t * p;
			document.getElementById("a").value=t;
			document.getElementById("b").value=zc;
			document.getElementById("c").value=mj;
		</script>
	</body>
</html>
